Posted
by
samzenpuson Wednesday September 03, 2014 @06:43PM
from the no-waste-zone dept.

Zothecula writes The problem with nuclear waste is that it needs to be stored for many thousands of years before it's safe, which is a tricky commitment for even the most stable civilization. To make this situation a bit more manageable, Hitachi, in partnership with MIT, the University of Michigan, and the University of California, Berkeley, is working on new reactor designs that use transuranic nuclear waste for fuel; leaving behind only short-lived radioactive elements.

Lets not forget the gov't research labs -- it would be nice if the U.S. gov't didn't shut down such research to appease an ill-informed political interest group.

Otherwise known as "the electorate".

No. Otherwise known as one particular political party's minority that has disproportionate power during primary season. Something very far from the electorate at large. Not to suggest the electorate is well informed on matters of science and engineering, but those few with deeply held political beliefs take scientific denial and misinformation to a new level.

Both political parties have their respective science deniers who will "primary" candidates who don't tow their line. Deniers have their respective a

The proposed reactor design sounds a bit like the EBR-II at INEL, formerly the National reactor test site, with the design also referred to as the Integral Fast Reactor. This program got shut down in the 1990's, though stories have been told about people who were sent out to Idaho to shut it down came back as converts to the cause.

No Nuclear is bad and dangerous.Actually this is not new. Many reactor designs that do this have been tested over the last few decades. Also fuel reprocessing does much the same thing. You are left with a few highly radioactive elements with short half lives. Some of those elements could be used for research and some could even be used as power sources in RTGs.

Not a problem if Japan can just its own waste. If it works, everybody else will want one of these reactors too. What the US or Russia tthinkf pf this will be of no consequence.

Most transuranic nuclear waste comes from making plutonium weapons - which Japan doesn't do AFAAK. Nor do all but a handful of states - if that many. The rest comes from the ca. 1% of spent nuclear fuel from NPPs that is transuranic - and that is almost completely Plutonium and will be taken out of that sliver anyway if reprocessed.

I don't think they do so in the breeder cycle - their neutron loss margins are fairly thin, hence why most designs propose extracting at the Pu-238 step (unusable for weapons, but great for space batteries). The burner cycle might be better in this regard. Fast reactors are able to do it, they have plenty of neutrons to spare.

They don't, but the ratio of absorption to fission in the thermal spectrum for them is pretty bad, so that can mess up your neutron budget. Depends on the exact composition, though - each reactor produces a slightly different mix and that makes the TRU content in spent fuel fairly heterogeneous, which complicates reactor design and makes fabrication of reliable fuel fairly expensive (hence why MOX fuel only contains the Pu content, not all the other TRUs and even so it's much more expensive than fresh Uranium fuel).

I was confused about the use of water and burning Actinides because I believe it requires fast neutrons to occur at a high rate and water is a moderator. Also, if water getting out of the way lets the reaction rate increase, the void coefficient would be positive? I'm not sure which mechanism they intend to operate to burn the Actinides, but it sounds like they're trying to push derivative technology as being a safer, more reliable road in terms of tooling and design. This explains nothing of how the rea

I was confused about the use of water and burning Actinides because I believe it requires fast neutrons to occur at a high rate and water is a moderator. Also, if water getting out of the way lets the reaction rate increase, the void coefficient would be positive?

It's a good point. I thought using water for a fast neutron reactor was something we had already moved past and were now considering using liquid metal, like lead, as a coolant with the reactor moderated by the design characteristics. Especially

If you have a strong enough neutron flux then you can burn the waste (i.e irradiate it until it transmutes to something with a short-enough half-life). Unfortunately, only fast neutron reactors have neutron balance good enough to allow a significant fraction to be diverted for uses other than supporting the chain reaction.

I never quite understood the allure of ADS. To my eyes it just looks like an exceedingly difficult way of achieving criticality. Given a good design, a reactor will self-regulate by its own negative temperature coefficient, so an external driver isn't strictly necessary and shutdown can be performed by passive systems that are equally dependable as cutting power to the accelerator, e.g. by suspended or spring-loaded SCRAM rods. There is the interesting proposition of not having to reprocess the fuel when running a thorium breeder cycle in order to extract the bred fissile and load it into the core, since one can boost the neutron budget externally, but that needs to be weighed against the pretty steep cost of a high-powered accelerator (in terms of current, not just particle energies) and accelerator reliability issues.

Don't think accelerator reliability issues are much of a concern any more, the systems are pretty mature at this point. I see the many advantage in being able to produce tailored neutron energy spectrum to process as much waste as possible.

The latter is the main focus in my mind. Excess energy is just an added bonus. We need a process like this as burying the nuclear crap has become a politically untenable.

I agree that burning the crap off is a good thing, but why tack on an expensive piece of extra equipment when pretty much the same effect can be achieved by being smarter about core design? I'm just not seeing the big advantage here.

I agree that burning the crap off is a good thing, but why tack on an expensive piece of extra equipment when pretty much the same effect can be achieved by being smarter about core design? I'm just not seeing the big advantage here.

By all means, let's move forward on the smarter core designs. However, we still have lots of waste from the older cores to deal with.

Another huge problem is that they have no idea what to actually use to contain the coolant loop.

Lead and Lead/Bismuth coolants are VERY corrosive and require active purification in order to keep oxygen levels down to incredibly low levels. Otherwise it'll corrode steel in a matter of weeks.

There are several proposed alloys or coatings but as far as I can tell none of them have made it past initial research phases and all have their own downsides. Like, one may have good thermal characteristics but h

Except that they aren't safe. Even though they are subcritical, they'll still contain plenty of fuel. So there'll be more than enough decay products remaining to cause a meltdown in case of the coolant loss accident.

Nuclear waste is only a problem if you have a massive misunderstand as to the scale of the waste. We're not talking about literal mountains of waste, we're talking about under 100,000 tons - for all of it from the USA since forever. You can do one big project and store all of it, nearly indefinitely. The story of Yucca Mountain is what happens when you have to involve people that want a project to fail instead of just getting the damn thing done.

>Nuclear waste is only a problem if you have a massive misunderstand as to the scale of the waste.

Incorrect, sir. Nuclear waste is only a problem if you have a massive misunderstanding as to the thing you apply the label of nuclear waste. For it is not nuclear waste, it's unspent nuclear fuel.

It would be foolish to build a massive pointless structure for nothing. Nobody's moving their nuclear "waste." It's not even waste to begin with. It's fuel.

Have you ever heard of a Molten Salt Reactor? The most famous one I know about is the LFTR proposed by Kirk Sorensen. These types of reactors also burn existing nuclear waste, but they do so at atmospheric pressure, and are inherently safe. See: http://www.investing.com/analysis/thorium:-an-alternative-source-of-energy-224358

We could build MSRs on site, so the fuel never has to be transported anywhere. Then we decommission the old dangerous water-based plants and run the safe waste-consuming molten salt reactors.

OCCUPY CARSON CITY presented this idea to the Nevada Committee on High-Level Radioactive Waste 7/2012. https://www.leg.state.nv.us/Interim/76th2011/Committee/StatCom/HLRW/Other/ResponsestotheSOR.pdf

This article confuses me because the Hitachi design is terrible. It uses pressurized water, which introduces all sorts of problems. The Molten Salt design is obviously better. I guess we'll just have to wait until 2020 to see how China does it.

Nuclear waste is only a problem if you have an agenda to make it one. Scream about the evils of reprocessing and the long life stuff piles up, eventually making nuclear power uneconomical. Perhaps that's what some people had in mind from the beginning.

Humm, let's see.U-238 absorbs a neutron becoming Np-239 then decays to Pu-239Pu-239 has only a 2/3 probability of fission upon neutron absorptionWater also has the tendency to absorb neutronsIt's no wonder that no TRU burning reactor has been proposed that uses water or helium for cooling, it's always sodium, lead or molten salt as coolant.

Also weird, is Hitachi already has a TRU burning design, the S-PRISM (GE/Hitachi project). Fast sodium reactors are actually known to be workable for that job.

It's possible they plan to only burn stuff beyond Pu in there, as that can already be consumed in MOX (which however produces more of the higher TRUs for the reasons you noted). It's really hard to tell what they're trying to do here without more detailed data on the actual fuel composition.

Also weird, is Hitachi already has a TRU burning design, the S-PRISM

It's possible they're having trouble getting a dedicated TRU burner design approved and built (there might be little economic incentive and much public opposition to new nuclear plants, no matter the safety of the techno

Any water cooled reactor is inherently less safe than a metal or salt cooled reactor.Water/Gas cooled reactor = high pressureAnything else = low pressureFully passive safety has been demonstrated with sodium and molten salt reactors.While AP1000 can be shutdown and kept cool without active safety systems, it does require lots of complex active systems while in operation.Still, non sense.PS: Any design that claims to burn TRU must be able to fission at least all transuranics. Any really great design will pur

I'm not a fan of light water reactors either, but you need to understand that the public isn't aware of the details and intricacies of reactor design. To them terms which make an engineer cry happy like a little girl, don't mean anything. I mean FFS most of them still think nuclear reactors can explode like atom bombs. They saw Chernobyl and Fukushima, they saw "boom", it's a nuclear reactor, therefore "nuclear boom".
I also think and hope education can change that, but that's a long road ahead and TRU-burn

Seems like a stream of protons (which is really just hydrogen ions) could be fired at nuclear waste to get it to split without making the next thing down the chain so neutron heavy as to make it radioactive itself. I would like to know how boiling radioactive waste is supposed to drop the half life. If it does I have some physics to brush up on.

I guess I should ask what you mean by "pretty sure". Adding to large atoms are a lot easier than small ones. It's been a long time since I've read about it, but it's called "proton induced fission". Admittedly, most of the reading when you Google it is a bit heavy. I do know that if you crack U238 with a proton that all 3 daughter isotopes have a half life of 35 days or less (one is like an hour and a half) and their daughter isotopes are all stable.

Clean power that can bridge capacity/fluctuation problems of solar and wind is just what we have been waiting for. I hope all the world governments tax rebate and finance the heck out of this to bring it to market in time to make an impact on worst effects of climate change.

Had to google the abstracts of the report and its conclusions are highly interesting. They claim to be able to breed at a ratio slightly above 1.0 in a BWR and even slowly consume TRUs by 10% per reprocessing step with unlimited reprocessing capability. Results of the report [epri.com]:

The analyses collectively indicate that the two reactors appear to be able to achieve their design objectives: The RBWR-AC provides an equilibrium-cycle breeding ratio of slightly above 1.0, thus providing for a self-sustaining fuel cycle in which depleted uranium is used for the makeup fuel. The RBWR-TB2 is capable of unlimited continuous recycling of TRU while consuming on the order of 10% of the loaded TRU per recycle (after accounting for the newly generated TRU). Most results confirmed the values estimated by Hitachi. Some differences among the predicted reactivity coefficients need to be evaluated further.

This has the potential to be a game-changer if true, as we could simply use existing reactor designs such as the ABWR (of which there are several operating already) to both burn waste and breed fuel indefinitely from U238 feedstock.

Is that this is another solid fuel, boiling water reactor. Which means they have all this Rube-Goldberg-esque over-elaborate over-engineering to control the plant in a shutdown state. And if they miss even one little thing, boom. Steam explosion.

While burning up existing reactor wastes is a Good Thing, there are better, simpler, safer reactor designs for things like that.

It's mostly a United States problem that waste isn't reprocessed. This is now and has been done on an industrial scale in Europe and the U.K. for several decades. For some reason the United States, under the guise of non-proliferation, will not permit reprocessing of spent commercial nuclear reactor fuel.

The story in this article isn't news. Everyone knows how to reprocess spent fuel since before the 1960s. What would be actual "news" is the time at which the United States allows the well-proven, industrial-scale reprocessing to be applied to its own reactors.

Even Canada does it. The United States' nuclear energy policy is laughably stupid. It's a shame, really.

It's mostly a United States problem that waste isn't reprocessed. This is now and has been done on an industrial scale in Europe and the U.K. for several decades. For some reason the United States, under the guise of non-proliferation, will not permit reprocessing of spent commercial nuclear reactor fuel.

Nonsense. Any company that wants to open a fuel reprocessing plant can do so, they just need to apply for a license and be willing to pay the bills.

Perhaps you mean that the U.S. government has decided not to run a fuel reprocessing plant at tax payer expense that produces fuel that no one will take unless paid upfront, and few can use anyway? There are no commercial fuel reprocessing plants anywhere in the world because they cannot make money, only spend it.

Well seeing as the US government took a huge amount of money from the nuclear generators over the years to fund a waste storage repository (which they are being sued over because of their utter failure to hold up their end of the deal) perhaps they could use that to pay for reprocessing? The electricity producers (and in turn, therefore, consumers) have already paid for it, taxpayers don't need to be involved.

Isn't burning waste what fast breeder reactors do ? They already did this but it didn't make it somehow. Superphénix for example had a few technical issues but still managed to be commercially exploited for a time. If was shut down for political reasons.The current stand is to use reprocessing and MOX fuel.

Fukushima's error was that they didn't raise the sea wall like many recommendations had told them too. They whole design is different, it's not really comparable.

Not just the design but many other relevant circumstances too. I drove past San Onofre yesterday, currently inoperative. Noticed the really big hills immediately behind it. Putting backup generators and such on that higher ground might be useful too. I'm not 100% sure but I think backup generators were stored at the nearby US Marine Base, Camp Pendleton, and the Marines would helicopter them in if and when needed. If so on high ground, secured and mobile. Might be a better idea than more walls. Other coasta

The area is periodically inundated by tsunamis. That would fit most definitions of a "flood". If Fukushima wasn't flooded, then neither was Noah, since that was salt water too.

The problem wasn't glaring except in hindsight.

Nonsense. Plenty of people thought it was a problem before it happened. The area is hit by a big tsunami about every 300 years. There are historical records of the last few, and geological sediment records of many more. The last one was 300 years ago. They were due.

I agree with your first statement, and I agree that Fukushima should have been prepared for that size of tsunami, but seriously.

The last one was 300 years ago. They were due.

THAT'S NOT HOW STORM FREQUENCY WORKS

Seismic zones do however show patterns of periodicity of varying degrees of regularity. There is an underlying physical mechanism accumulating stress, and faulting must be triggered within a finite time limit given the finite strength of the fault zone (but may trigger sooner). Chances of a great earthquake absolutely do increase with time, dropping to minimal only after each major event.

That's not what "flood plain" means. A flood plain is an area frequently inundated by a river. Else everything under about 1000 meters is technically flood plain (from nearby several km asteroid impacts).

Nonsense. Plenty of people thought it was a problem before it happened. The area is hit by a big tsunami about every 300 years. There are historical records of the last few, and geological sediment records of many more. The last one was 300 years ago. They were due.

Plenty of people knew including the builders of the plant who had constructed seawalls capable of withstanding a tsunami about 5 meters shorter than the one that actually hit. What they didn't know until much more recently was that tsunami could be considerably higher than the original 1 in a century events

That's not what "flood plain" means. A flood plain is an area frequently inundated by a river. Else everything under about 1000 meters is technically flood plain (from nearby several km asteroid impacts).

Fukushima Daiichi is actually on a flood plain though. It is on an extended coastal sea-level estuarial marsh plain deposited by a series of rivers coming down from the mountains. BTW - there is no "frequent" required. Flood plain maps mark 100 year and 1000 year flood boundaries, something on the 1000 year boundary is still on the flood plain, even though that part floods rarely.

Noah wasn't in a flood because that is a fairy tale...
Also the definition of "Flood Plain" may differ based on location. Where I live it is a legal term used as a covenant on property to distinguish land at high risk of regular floods (usually from rising rivers/poor drainage, so as to advise both potential buyers and insurance companies of risk. I'm not aware of any coastal property falling under this definition.

Yes it is. Take a look at this US Army topo map [utexas.edu] (the latitude is (37.427 degrees, its on the coast). It is on an extended flood plain stretching along the coast, created by several rivers (Takase, Maeda, Kuma. Tomioka, etc.) . The whole area is a sea-level marsh consisting of soil deposited by these rivers at flood.

The problem wasn't glaring except in hindsight.

Because, you know, no one had ever seen a tsunami in Japan before. Oh wait, tsunami is a Japanese word. That doesn't seem quite right, does it?

Japan had fifteen of them since 1900 [stfrancis.edu], before Tohoku (the slightly dated linked list misses the 2007 Niigata tsunami).

The plant is on a bluff which was originally 35 meters above sea level. During construction, however, TEPCO lowered the height of the bluff by 25 meters. One reason for lowering the bluff was to allow the base of the reactors to be constructed on solid bedrock in order to mitigate the threat posed by earthquakes. Another reason was the lowered height would keep the running costs of the seawater pumps low. TEPCO's analysis of the tsunami risk when planning the site's construction determined that the lower elevation was safe because the sea wall would provide adequate protection for the maximum tsunami assumed by the design basis. However, the lower site elevation did increase the vulnerability for a tsunami larger than anticipated in design.

Not considered in the above would be the simple yet modestly more costly possibility of obviating the need for a sea wall by preserving the bluff and setting the reactors back, using modestly sized canals to cycle the sea water to and fro. That, naturally, wasn't the cheapest conceivable option, so it didn't survive the bean counters. Instead, they removed 25 meters of foothill, a feature that was originally 2.5 times the height of the tsunami before they fucked it up. The whole `bedrock' smokescreen is easily dismissed for the lie that it is; they could have reached bedrock from a setback design with no more difficulty.

This was done for one reason; grading the beach provided cheaper access to the ultimate heat sink, sea water. Less construction cost, less pumping, less maintenance, etc. This isn't lost on the perpetrators either. They know [japantimes.co.jp] they're at fault and they knew it at the time, whatever lies they tell today notwithstanding.

This isn't speculation, either. Fukushima Daini did not get submerged, did not melt down and did not contaminate the land and the sea. Why? Primarily because it was built at higher elevation, [thebulletin.org] which is about the only significant difference between these sites.

soil and bedrock composition is probably different in California, but their Diablo Canyon plant is safe from Tsunamis, set up on a 30 meter bluff. It also has a gravity-fed emergency cooling pond, and is internally reinforced against earthquakes. The bean counters didn't win that one.

As other's have pointed out you don't address how you preserve earthquake resistance, and quite frankly unless you're a civil engineer or reference one I don't give what you say much weight anyway.

You ignore the horrendous cost of earthworks involved in the modification. And then on top of everything you assume that a 25m change makes even a tiny bit of difference in a multi-billion dollar project. Sorry but access to the sea water due to the extra distance would have been los

It wasn't even the seawall height that was the real problem, since any seawall could eventually enounter a larger tsunami than it was designed for. Even the old reactor design used there is very forgiving in the sense that if the plant totally loses power after being scrammed and the backup diesel pumps don't work, you have plenty of time to connect an external coolant water source to the reactor and pump water through it for a few weeks to pull away heat of decay.

Will these new elements have significantly shorter half-lives? Will they themselves be able to function as fuel and could thus further be changed?

If both of these are true, even if they're still transuranics, then wouldn't it make sense to build a few of these reactors in geologically-stable areas?

We know the causes of the three biggest nuclear disasters, one being a maintenance task that went awry (TMI), one being an ill-considered test that led to meltdown (Chernobyl), and one being a natural disas

In general the waste from a 4th gen reactor design is cited as being hazardous for a few hundred years. Something manageable, unlike the current situation where we are looking at tens of thousands of years.

Mmmmmm, no, you can definitely burn up transuranics and you pretty much HAVE to end up with less at the end of the day, but the question is whether or not you have LESS OF A PROBLEM at the end of the day because there are plenty of "short lived" radionuclides that you really would rather trade for some nice plutonium or americium. On top of that the entire structure, premesis, possibly nearby things, etc will become waste, and even low level waste is costly to deal with. This is the same sort of set of issues that have made it totally uneconomical to reprocess spent fuel. ANY handling is messy, dangerous, and produces a lot of expensive to dispose of waste.

To me it seems a no brainer that option B makes infinitely more sense. The proliferation risks are honestly marginal, considering the alternatives. (increasing reliance on coal, or a never ending stockpile of option A. (So much of it in fact we're considering boring a hole in a goddamn mountain to stuff it into.)

Exactly! In terms of expense of dealing with radiation 100 years and 100k years isn't that much different from our perspective. In either case you want to contained, well contained. Honestly, transuranics are surely more expensive to house to some extent, but the question is if the extra cost is more than the cost of burning plus cooling/disposal/cleanup of these high neutron flux reactor designs.

You are right. The ignorance of many people on the subject of radioactivity is amazing. I don't know why, maybe because nuclear seems magical. But the radiation produced by an isotope is inversely proportional to the half life. People complain about nuclear waste that will be radioactive for a million years. Sure but that stuff is pretty safe because of that long half life it doesn't produce much radiation. It's the short lived isotopes that are really dangerous because of the amount of radiation they put o

" On top of that the entire structure, premesis, possibly nearby things, etc will become waste, and even low level waste is costly to deal with. "Umm no.The reactor and some parts will become low level waste not the entire structure.Everything is costly to deal with the dismantling of a solar plant or wind mill is costly to deal with how costly?This post is full of vague statements and errors designed to instill fear without knowledge.

What is "neutron saturation transmutation"?
I'm also skeptical of their claims, as it appears to be a thermal-spectrum light water reactor and it's quite difficult to consume TRUs completely in the thermal spectrum, the neutron absorption cross sections are fairly large. Maybe they've got higher enrichment and so shitloads of excess reactivity, so they can afford to lose the neutrons, in which case I seriously hope they have a strong negative temp coefficient. Don't know, would be good to learn the details.
Not sure about the likelihood of meltdown being increased, though. I don't think the decay heat profile of MOX is significantly different from regular enriched Uranium fuel (decay heat melted Fukushima fuel, not fission heat).

Nuking it until it glows. First you separate your waste into constituent elements (their oxides, whatever) then you irradiate it with neutrons until most of the medium-level waste transmutes into something with a short enough half-life. You can optimize it a bit by playing with neutron energy to maximize the capture by most problematic isotopes. The size of neutron capture cross-section is not an issue, since you don't need those neutrons to support a chain reaction.

The concept is pretty old, but requires a shitload of neutrons (since you typically need to capture multiple neutrons to transmute a single waste atom). The only practical way to get that much is to use a fast neutron reactor. And even then it's marginal. In future, when we get fusion reactors, fusion neutrons could be used much more economically for that.

The Hitachi press release contains absolutely no information about what might be new, unusual, or effective about their approach. They mention an undescribed new fuel core in passing, that's it. It would have been helpful if they had included something to give the sense that it is not pure hype.

It's never been cost effective. The same way safe coal mining and 100% safe fly ash disposal isn't cost effective. If you need to expend more energy to deal with the waste than you get out of it, it's not worth it.

....but what does the "short-lived radioactive elements" dissolve into? surely not *nothing*?...how much can we strip away through processes before every part is used?...how little matter do we need left over before we can eject it from the Earth's atmosphere into the Sun?

If we get it to the point that it's economical to launch in a rocket, then there's so little left that storage shouldn't be a big deal. And if it's safe enough to put on top of a rocket, then it doesn't need to be removed from our biosphere.

Most of the really radioactive waste is extremely dense. So it gets insanely expensive to get it out of earth gravity well. To make matters worse, we have no space launch systems that are reliable enough to use for this type of disposal. It's one thing to have a bunch of highly radioactive material sitting around in a shielded location. It's an entirely bigger problem to have a failed launch blasting toxic crap all over hundreds or thousands of square miles/kilometers.

It's also a waste of of non-renewable material with a high amount of potential energy that we may be able to do something with sometime in the future as our understanding of physics progresses.

Even ignoring the huge amount of energy required to launch something into space, our current launch vehicles are not the most environmentally friendly mode of transportation either.